The process of a transaction being created and included in the blockchain is as follows:
The sender creates, signs, and broadcasts the transaction
All Bitcoin full nodes, including miners and regular users, receive the transaction and validate it by making sure it follows the Bitcoin protocol rules
Nodes temporarily store the unconfirmed/yet-to-be-mined ...
Its the time the wallet was last synchronized to, it won't know about any transaction changes in or out past this time until it has been loaded again by a synchronized node. It has nothing to do with your transactions specifically.
A reindex will not redownload the block. However, after safely shutting down Bitcoin Core, you can delete the block file containing that block. When you start it again, you will need to reindex, but once it gets to the blocks that you deleted, it will redownload them.
When a miner validates a block, does the block contain all transactions in Bitcoin for that time period?
See this question for info about the structure of a block.
A block can contain up to 4,000,000 weight units worth of transactions. So the miner can select transactions to include in the block, up to this limit. Generally, the miner will select the ...
For this task, it's better to run a full-node with the transaction indexing txindex=1. Then you can get the number of confirmations from the txid of a transaction by calling:
bitcoin-cli getrawtransaction "txid" true and checking under the field confirmations. If you have jq installed you can call for example bitcoin-cli getrawtransaction ...