Yes dear, there are 3 attempts for JEE Mains, thus if have filled JEE form in 2017 & 18 then you have left with one more attempt, but you can't appear for JEE Advance.

Yes you can apply because as per the norms of JEE, 2 years of drop is allowed but not more than that. You will not be able to appear for JEE next year as it would be your 3rd year of drop. So participate in counselling and IIT, NIT or IIIT would be decided by your rank and score. I would suggest you to get into a college as per your marks because you won't be able to apply next year even in private colleges as they ask for JEE score. 

Goodluck

Well, from my last exam date whixh is 2017, you can give JEE mains three times.

Hence, you are allowed to give paper till 2019.

This will represent, you are allowed to appear in JEE mains 2019.

Since, if you have given the paper and been alloted a rank accordingly, then it reflect you can appear for JoSAA provided you have a decent minimum percentlie to appear in that.

Thank You