Once received Green Card, can I leave the country and come back in? or do I need to apply for something else?

You do not need anything else as long as you do not plan on staying out of the US for more than 6 months. All the best.

We are Canadian citizen's looking for a legal way so that my wife and I could stay in Florida full time or a 5 year term?

You should either have a immediate family member that is a US citizen of LPR or an employer who will file your green card or visa or you could get...

From the information you have provided, not it most likely will not affect the PERM application.

How many days i still have to find a new job who can sponsor my h1 next year ?

Rule of thumb is you can only unemployed for 90 days on OPT. All the best.

How "90 days unemployment rule" is calculated during OPT extension application?

You can find answers to all these questions on the USCIS website or by talking to your school's visa co-ordinator. All the best.

Am from jamaica I live in the usa now just got married I don't get my legal status at this moment can I travel to porto Rico my

If you are travelling to puerto rico when you have a valid visa, you may be able to travel. All the best.

H1B Transfer while H4 EAD is in process

No, the transfer does not affect your EAD process, as long as it does not get denied. All the best

When will get my result for mtr

Check the USCIS website to find out the current processing times for MTRs, they change often. All the best.

Do I need a Birth Certificate for my mother?

Yes your mother will require a birth certificate for almost all of her immigration petitions. All the best.

Any issues in IV process through home country due to not completing STEM extended period and leaving job in US?

From the information you have provided, it seems like he will not have any issues leaving the US.