I installed xf86-video-intel-2.99.917.916_g31486f40-1.2.x86_64 (build date 2021-05-27, i.e. updated more than once). All the listed misbehaviors are gone, same as for regatos' version 3.0. Thanks for expediting the new Intel version, and sorry for not checking it right away. This bug can stay in fixed status.