Continued inability to pay your installments for any reason constitutes a default on your loan. At this point the bank/lender can demand a payment of the full outstanding amount of the loan. The lender can also serve a legal notice on the borrower and in case of secured loans, acquire the loan security (property car etc) and try to dispose of the same to recover their money.
Yes, in some cases you can. You need to inform your bank in advance. This should only be for a few days and you will have to pay delayed payment charges. This will still impact your credit rating.
Delaying your installments frequently may affect your credit profile and might make further borrowing not only difficult but costly too. However, in some rare circumstances, if you delay an installment, most banks would charge you a delayed payment charge, as high as 3%, compounded monthly.
Dishonoring a cheque is a criminal offence. Legal actions may be initiated against you and your credit profile could be seriously damaged.