1.D borrowed P30,000.00 from C. To secure the debt, D pledged his ring, wristwatch, and necklace. Before the debt could be paid, C died leaving X, Y and Z as heirs. By agreement among the heirs who inherited the credit, the ring would secure the share of X of the credit, the wristwatch the share of Y, a necklace the share of Z. Later, D pays X P10,000.00. Can D demand the extinguishment of the pledge of the ring?

2.X, at Y's request, executed a Real Estate Mortgage (REM) on his (X's) land to secure Y's loan from Z. Z successfully foreclosed the REM when Y defaulted on the loan but half of Y's obligation remained unpaid. May Z sue X to enforce his right to the deficiency?

3.A shops at supermarket, buys groceries worth P1,000, and pays with an unfunded check and goes home with the groceries. The check is dishonored for lack of funds. Is there estafa?

4.Please refer to number 3, if the grocer, knowing A, allows him to pay on a later date, granting then only credit on the goods, and after a few days, A pays with a check that eventually bounces. Is there estafa?

Please cite the specific article so I can double check.