I am currently in chapter 3. Is it possible to get them now?

They are:
A Long Way from Home
A Restless Ghost
Bloodthirsty Vegetation

Of the three, only "Bloodthirsty Vegetation" can be done in chapter three. The quest givers of "A long way from home" and "A restless ghost" are no longer at their locations. The Coccacidium, which you need to kill in order to complete "Bloodthirsty Vegetation", still spawns in chapter 3. Once you've killed it, talk to Vincent and he'll tell you to go to the Royal Huntsman.

I found a lot of information on Witcher Wikia. But careful with the spoilers, they can ruin the fun. It usually warns there about the spoiler section, but they aren't hidden, so it's easy to catch some part of them.

That wikia site even has checklists for all the chapters. The quests you've missed are very minor, the only one that matter is the trophy quest, and then it only matters if you manage to get all of them (won't say why for the spoiler sensitive). The odds of doing that on your first playthrough without a checklist or wiki site is kind of low, imo.

I am using the wikia to make sure I get all the quests. Unfortunately, that was after I started chapter 3. I didn't know that there's a checklist, thanks for telling me. I'll start using it on my next playthrough.