yes you can apply no problem

HIiii

The eligibility for JEE exam is qualifying class 12th exam with PCM with minimum 50%. So yes you are eligible for JEE Mains.
For JEE Advance, you are supposed to qualify JEE Mains with top ranks and to get admission in IIT you must qualify JEE Advance.
Talking about the difficulty level, The competition is very high for these exams so it has to be a bit difficult so that the deserving candidates make it to the top.
Well, prepare well, study smart and be focused and dedicated.

Good Luck.

Thanks!!