Three questions need answers

Hello guys!

I'm new to this forum and can't be sure about correct posting the question. Anyway it will take some time to get used to local rules.

The sentence is taken from context where no info about any sea was mentioned. The only data present is that we read about Gdansk situated in Poland.

1. The first question is do I have to use "the" or "a" before seashore: "Nowadays its hospitable atmosphere welcomes tourists from different countries to walk by its adorable streets, to look at its historical interiors, to rest on the (a) seashore or to go by sea in a sailboat."

2. The second question is do I have to use "to" with all the verbs going one by one through commas or maybe it is possible to put it only before the first verb?

One more question is from another sentence.

3. Is it possible to use "after" without further explanation? The previous sentence tells us that the restoration took place before and then we explain that tourists may visit some places which were opened after... Will it be grammatically correct or should we reconstruct the sentence?

"All you can see here today is a result of long and careful restoration. Now tourists may find workshops, galleries and cafes here which were opened after to offer exclusive and interesting stuff."

I will be thankful if you will mention any other mistakes found.