Yes, you can start your renovation immediately after you have collected the keys to your brand new house BUT be reminded of the followings:-
1) you are not allowed to reside within the house; and
2) make sure that all the defects has been rectified by the developer because the defect liability period will be expunged once you meddled with the house, especially wirings.

Remember to get approval from the Joint Management Body.

Good luck.

Yes, you need to make a formal application to them and then pay the renovation deposit before they will issue to you a temporary permit to renovate otherwise your contractors will be barred from entry.

You can take back the deposit once the renovation is completed.

technically speaking, you still need to "inform" the JMB on any works carry out in your parcel however most people just ignored it because it does not involve acts that will cause nuisance to your neighbors (drilling etc).

the "informing" is actually for everyone's safety because then people will know the people entering and existing your parcel are authorized people (you don't want people entering and exiting your home with your belongings now, do you?).

the "deposit" paid is to reimburse the JMB as repair costs in the event your contractors damage any of the common properties.

to me, repainting and change of lighting does not warrant for an inform.