When you cut a branch off, it will not regrow. Instead, growth will continue from bud(s) on the remaining part of the branch.

If that is what you were asking..

For the other questions I'll let others answer.

There’s some clarification of the nomenclature needed before discussing pruning. A cane is a stem which grows straight out of the ground eg a raspberry or Kerria. You can cut these off right to the ground and new ones will grow from the roots. Caning shrubs need this treatment every so often or you do get tall bare stems as you describe.

For a branching shrub, wherever you cut, new branches will grow from the dormant buds below the cut.

‘Standard’ has a specific meaning in shrubs ie a single straight vertical stemmed plant with a bushy top. So pruning a standard rose would be different from pruning a Hydrangea. Unless the Hydrangea too were a standard form.

i presume these are plants that are new to you this year ....

why cant you see where prior cuts were made.. they dont disappear ..

a pic would sure help us.. teach you the words you need to know ...

if we are talking about a plant that usually grows on the ground ... artificially lifted on a 'standard'... then the foo foo plant.. is grafted up at the top ... you do not want the flowers of the root system.. nor the long trunk ...

ergo ... you have to be sure not to prune back further than the favored plant ...

that said ... these type of plants have dormant buds ... so when you harvest a flower.. or prune back a branch ... those dormant buds will trigger .... and you are all set to go ...

lets see if i can find pix of such on a hydrangea .... close enough

https://surfinghydrangea.com/winter-pruning-of-multistem-hydrangea-paniculata-432

so .. use a search engine with proper terms.. and yo will be able to find pix of what you should do ...

ken