If you stay in high floor you don't need window grill, I don't think someone will wanna climb so high up and break in through the window

You can install some restraint to prevent the window from fully open, this should prevent kids from falling

Grill at the main entrance is still needed, you never know if other unit's owner decide to break in your house one day, and you can't remove the grill at main door if it is installed by developer

For push pull type window can install this
https://shopee.com.my/product/187096093/480...7784?smtt=0.0.9

Or this
https://shopee.com.my/product/169197130/284...3983?smtt=0.0.9

There is those for sliding door as well

Actually this is good even the is no children, because strong wind at higher floor can blow open a half open window, next thing you get is a flooded room when it rain heavily with strong wind, experienced it in my house before

i'm not using any since i have no kids and i stay alone, recently i also removed those grills that my parents installed when they buy the house

actually you can DIY, check the sliding mechanism of your glass window, then stick a piece of metal there to stop it from sliding hence prevent the window from opening wider

another alternative is to use nylon string or zip tie to tie the handle of both window so it cannot be fully open