i was playing with builds in prologue using bag of tricks mod and i created

human
Sorcerer crossblod 1
Elemental Witch 9
Winter Witch 5
Loremaster 5

and i can not get wizard Wizard spell selection it is listed on list of possible selections, but it's not listed on feat selection list, either there is a prerequisite that is not writen anywhere or this is buged?

Well Galaxy bugged to can't attach images so here's link since i can't submit bug report from gaem cos i use mods => https://ibb.co/smJxkB3

Can be a few things, but I don't know your complete build or the mod you use so I have to make a few guesses:
Do note that you started out as a crossblooded sorcerer, which receives 1 spell per spell level less.

Did you use the mod to level up to level 20 in one go? If so that might be the problem as normally you need to choose per level.

**Looking at the Pen and paper version of loremaster there might be another reason: Intelligence score.

While the sorcerer relies on a good Charisma score, lore master is a prestige class that relies on a high intelligence score. Probably more so than other spellcasters that is because your loremaster's secret do have an intelligence prerequisite.

It could be that your character's intelligence score is too low to pick the Wizard Spell secret.

Hmm it could be int, will check, thanx, even tho, it would be nice game would notify you about that, it does for combat feets like dodge etc that you are missing dex score and the feet is on selectable list just greyed out so you can't select it

The pen and paper version of the loremaster does mention it:

"Secret

At 1st level and every two levels higher than 1st (3rd, 5th, 7th, and 9th), the loremaster chooses one secret from Table: Loremaster Secrets. His level plus Intelligence modifier determines which secrets he can choose. He can’t choose the same secret twice."

I do not have the info about the game version of the class handy right now so I don't know if Owlcat changed the mechanics.

Another possibility is that you created a level 20 character using the mod, while the loremaster requires you to pick only one of your previous caster classes. Since (in essence) you have 3 previous caster classes the mod might have picked one class.

How is the spell slot progression of your other witch class? As caster levels of elemental witch and winter witch stack and you see that you have a number of spell slots and spells know similar to that of a level 19 witch the mod might have picked the witch class instead of your sorcerer class.

to sum it up: because the loremaster allows you to pick only one caster class to advance their caster level/, spell slots and spells known you can have two extremes: spells as a level 6 crossblooded sorcerer and a level 14 witch or on the other hand as a level 1 crossblooded sorcerer and a level 19 witch.

Just for test i now tried, and i am leveling the characters manualy, all i do with mod is dump 3m xp on them

Lvl
6 - Sorceres - crossblooded, silver dragon, watter
6 - Elemental Witch
5 - Winter Witch
1 - Loremaster

str 10
dex 16
con 10
int 18
wis 14
cha 16

So after i pick loremaster class with this setup (it is usles setup i know)

As Sorcerer i only get to chose wizard feat as secret
As Witch i only get to chose Wizard feat as secret

second atempt was

Lvl
1 - Sorceres - crossblooded, silver dragon, watter
6 - Elemental Witch
1 - Winter Witch
1 - Loremaster

str 10
dex 16
con 10
int 18
wis 14
cha 16

And again all i can pick is wizard feat

So either it does not work or i am not understanding how this should work

To be sure: the issue now is that you can only pick the loremaster's wizard feat secret right rather than no being able to pick wizard spell secret?

You ability scores are fine. You should be able to choose from more than one secret.

As link to image i originaly posted shows i can choose most combat feats, but not the spell feats, no matter what i do they never show as selectable feats

Could be a bug with the mod as I have no idea how you could have locked yourself out of those two feats without having them picked before.

I made my nenio a loremaster, and firstly, the first level did not advance her wizard spellcasting, is this intended? as per the tooltip it should be a full caster prc. secondly, i can not choose to select other spells, only the class secrets

Loremaster has spell progression at all levels.

Is your character a full wizard before picking up the loremaster prestige class?

Even though the loremaster is a full caster if you have multiple spellcasting classes you must choose which spellcasting you want to advance (per level) as the loremaster does not get spells of its own but should progress.

Also a loremaster does not grant bonus spells for a wizard; you must buy spells and write them in your book yourself.

In a later patch they seemed to break loremaster entirely, you have to have level 3 wizard and cleric spells which broke the class. Hoping they fix it soon

Both arcane and divine spells? Be sure to report it with the Alt+B report function.