HHmm.... I believe accelerating its gd to change gear in sequence.. but when your turning or slowing... its alright to jump from gear 4 to 2 when turning.. than back to accelerating in sequence..

Yes its possible to shift a gear without engaging the clutch.

I found out when I did that accidentally. I was dreaming one day when driving and accidentally shifted without engaging the clutch. It's possible to my supprised!!

Edit: I also found out that when your RPM is slightly above 1000rpm, its kinda easy to slot into first gear without engaging the clutch. the sweetspot is somewhere around 1200 -1300 rpm. but it depends on car though.

1st gear for normal cars, max red line around 50km/h straight go to 5th, turtle like u said
The best way is to rev to the optimised powerband then u shift gear, I heard it saves fuel because your car has enough torque to move already, the momentum is there so less working on the engine on higher gears

what I meant is you only shift gear when ur rev meter reaches to a point where ur torque is at the optimum level

for example, my Wira 2.5Krpm-3Krpm the torque comes, then shift loh