Change of Status from B2 to F1

Very unlikley that you will be granted a change B to F. Better possibility is to depart the US and seek F from outside the US.

What are my chances to get H2 tourist visa if I decide to meet my boyfriend who is on F1

If you are able to satisfy the US consulate of your non immigrant intent, it may be possible but not likely to obtain a B-2 tourist visa.

Can my children get British citizenship and a British passport?

Look for an attorney that is knowledgeable and eligible to practice in the UK

You may use it but it is up to USCIS to accept it. More likely a letter from NC will be accepted.

Yes you may request a re scheduling of the interview

Can i go back original H1b conditions if my ammendment was denied

Have the attorney that prepared the filings for your employer review your questions as the facts are important.

If i am on i485 pending status, and like to extend my h1b

If H-1B is not extended or extension properly filed and pending and you do not have EAD you are not permitted to be employed. You will be...

If not employed during the 90 days that is an issue.

Is joining date after 90 days of OPT start date a problem?

If underemployed during the 90 days y, yes that is an issue.

I-751 : Financial Documents

Best to submit the tax returns in accordance the the form instructions.