A1: re Library Updates: the principle is that these Updates are provided for those users who downloaded and installed the main library files some time ago. This way they only need install the Update, not the whole library again.
When an Update is released its files are also put into the main Library downloads.
So you should be OK not to download it. Or, you can download it from your User Area /My Products/SampleTank 4 section, UnZip it and compare the Dates Modfied with those of the files in the main library download.
A2 All additional SampleTank 4 library packs should be installed into your SampleTank 4 library. Just set it in the IKPM "Install to ..." menu choice. In fact, once you have installed the main ST4 library you might not need to set that choice, as IKPM may find it automatically (Disclaimer: I have not tried that
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