From which version does Safari not support 32 bit architecture?

Solution 1:

According to Wikipedia - https://en.wikipedia.org/wiki/Safari_(web_browser)#64-bit_builds - Safari has been 64-bit since Snow Leopard OS X 10.6 in 2009, which would be Safari 5, [around the same time they stopped supporting Windows.]

All Macs since then have been 64-bit capable, but until Catalina have been backwards compatible with 32-bit applications.
The last OS X to be capable of running on 32-bit architecture was also Snow Leopard, 10.6

The App Store will only offer you builds of Safari compatible with your Mac's hardware & OS
Safari 11 - 10.11 to 10.12
Safari 12 - 10.12 to 10.13
Safari 13 - 10.13 to 10.15
Safari 14 - macOS 11 [backwards compatibility currently unknown]