First of all, AmpliTube 5 ("AT5") is not released yet - it will be before the end of this year.
Yes, you will be able to just download it (using the IK Product Manager). It may well be with retailers later.
There will be different editions of AT5:
AT5 Custom Shop (will be free)
AT5 SE
AT5
AT5 MAX.
And there are also some bundled with hardware (AXE I/O
They differ in features and the gear models included. Halfway down this page:
https://www.ikmultimedia.com/products/amplitube5/there is a link to a comparison table and a link to a PDF comparing each edition.
AT5 SE, AT5 and AT5 MAX include an 8-track recorder. Please note that it is NOT an audio interface.
Some of the editions include bass amps - check out the PDF for the lit of amps in each edition.
Yes, it is one software program (or plug-in, to load into a Digital Audio Workstation).
We will try to help you here or you can contact
Sales/Account Support, via here. You will be able to search the FAQs first, but if they do not resolve your issue, there is a link at the top to a Support form. Sales Support for advice. Response time normally is within 2 working days (US (East Coast) Business hours, generally), but in the current circumstances please allow some more time.
After purchase and release, there will be a download link in your User Area / My products section under AT5 to the IK Product Manager ("IKPM") software program. Download and install that, then use it to download, install and authorise your purchased AT5. Run the AT5 program, configure it for your audio interface, plug in your guitar and off you go.
For the moment:
-- go to User Area / My products
https://www.ikmultimedia.com/userarea/my-products/-- you should see an entry for AmpliTube Custom Shop (this includes the free edition of the current version of AmpliTube ("AT4") with a Serial number to enable use of a small set of gear models)
-- download it, run the installer (which will install 3 programs)
-- also installed is the AT4 User Manual, which will give you a good idea about AmpliTube.
If you do not wish to do that you can just get the User Manual, if you click the red [Download Resources] button in the AmpliTube Custom Shop entry.
Hope that helps
But come back and ask whenever you want.