This question and answer forum is not meant to give such a verse by verse study of Scripture. However, if you wish to have such a study you might consider asking your pastor for (or ordering for yourself) a copy of the paperback book titled "Romans" from the People's Bible series (available from Northwestern Publishing House, Milwaukee, WI). This is a series of paperbacks on all the books of the Bible which give a verse by verse study of portions of the Bible such as the one you are inquiring about.

To give a short answer to your question, we could summarize Romans 9:10-21 like this. Really, we should also include the whole section 9:1-24 so that we have the whole context. The main point of the whole section = NO ONE EARNS SALVATION.

In vv1-4a Paul grieves for the Jews who have rejected God's salvation. In vv4b-5 Paul shows that God showered the Jews with eight wonderful blessings. In vv6-9 the point is that God did not say that all of Abraham's descendants would be his special people Israel. In vv10-13 Paul shows that it was only God's mercy that Isaac was chosen, not something Isaac had done to earn God's election. In vv14-16 Paul makes the same point that Jesus does in the parable of the workers in the vineyard (all the workers received the same pay though some worked all day and some only one hour) = when God shows mercy to some (like Isaac) even though they didn't earn it, no one can complain that God is unfair--all they can say is that it is a matter of God's mercy.

In vv17-18 Paul shows that God will harden some like Pharaoh who harden their hearts against God (so when God hardens some it is because they first hardened themselves against him).

In vv19-21 Paul speaks about a third group of people (1st group = those God elects in mercy like Isaac, 2nd group = those God hardens because they hardened themselves against God like Pharaoh) = people who are not believers but who did not harden themselves against God.

In vv22-24 Paul tells believers to look on this third group and also see God's mercy. Though they did not believe, God did not punish them immediately but bore with their unbelief with great patience (like the Jews Paul spoke about in vv1-4a). God's patience with them shows us again his great mercy.

The bottom line of 9:1-24 is that NO ONE EARNS SALVATION. Some receive it purely as a result of God's mercy in election (believers like Isaac). Some God hardens after they harden themselves against him (unbelievers like Pharaoh). Some do not believe, but God bears with them patiently in his mercy even though they merit his immediate judgment (unbelievers like the Jews).

For the details on these verses confer the paperback book noted above.