Can my husband and I file our taxes together?

You can file your taxes together. Probably should wait till you get employment authorization. I assume you applied for it. It takes 90 days and...

I reached USA on APR 2, At the port of entry officer had look at old visa and provided I-94 date instead of new visa.

Go to the nearest customs and border protection office usually at the airport and they may correct the error.

This is standard procedure reviewing your file. Do not leave the country before you get your PR card unless you already have advanced parole

Can F-1 student marry US citizen in Mexico?

I would not try renter without a valid visa. I would also not renter on a student visa after you are married as it may be evidence of visa fraud as...

1) Will it be okey to travel out of USA leaving my pending adjudication? 2) How long it ll take to make decision?

you can return any time before your advanced parole expires but if your case is denied then your parole is revoked and you will not be allowed to...

No your borther cannot complete it. The joint sponsor must be a permanent resident or US. citizen

L1A expiring, EAD and travel document pending. Legal stay valid?

You can legally stay if all are filed before your L1A expires but you cannot work after L1 expiration until you receive your EAD

Will this affect once I file to renew my work permit with immigration?

I am not sure if you are saying charges were or were not filed against you. Regardless it wont effect renewal of your work permit

Whether above documents are sufficient to proof my employment with them?whether is it mandatory to show 8.5 yrs of experience ?

You only need to show 5 years of experience for EB2 and a Bachelor degree. you can provide your salary stubs and w2

My sister is UK citizen and I need help to get information about UK visitor visa

This site only deals with USA visa issues