Answers as below :-

1>Yes they can send back within that period on whatever reasons example non-performance of duties or assigned targets is one of them

2>Yes -employer can do that

3>2 years you cannot enter on work visa but need NOC to comeback on another visa . You can come back on business visa though and have UAE RP stamped .Direct hire or indirect makes no difference , if you have good business relations with your boss , you can get NOC thatz all-in plain simple language .

4>You at no stage can demand an NOC as NOC can be sought strongly -if you have not rcd your salary for last 3 months or more or if you have been harrased in any manner only .
Otherwise NOC is employer's decision wholly -to give or NOT .

5>You get only gratuity which also is limited to 40 days if worked more than 5 yrs or 30 days of basic salary if you work less than 5 years + annual vacation salary if it is due at that point .

Hope all your Questions are addressed .

But highly appreciate , the way you have framed the Questions . You left no stone unturned to find out , how to get out of existing contract and get another job in Qatar . All the best .