Betta Fish: Tips for keeping a male betta fish (ASAP please)

Hi everyone, I need a crash course on how to keep a betta fish. My friend is giving one to me tomorrow as she cannot keep it anymore. I've done quite a bit of research, but just want to make sure I'm not missing anything out. 
 
What I know so far is: 
• 5 gallons minimum, though some owners may go down to 2.5 (wide instead of tall tank to allow the fish to swim along the surface more) 
• Need a lidded tank but leave an air gap
• Heater 25.6 to 26.7 degrees Celsius (for when I turn on the aircon) 
• Try to have some aquatic plants with big leaves to allow the betta to rest.
• Any decor must be smooth to avoid ripping the betta's fins. 
• 10-25% water changes weekly
• Dechlorinated water, PH between 6.5 to 8 
• Feed twice a day, about 3-4 pellets.
• LED light for aquatic plants
• Low power filter – very gentle water surface agitation, with floating plants to provide shade from the light and disrupt the surface agitation of the water

I'm planning to get: 
• A 4 gallon tank (this is the biggest my room will allow) 
• Betta / protein pellets (1mm width)
• A waterfall filter (the lowest powered one I can find?) 
• An automated heater 
• LED light
• Aquatic compost, root tabs, gravel
• A small structure wood to place inside the tank
• Big pebbles (to anchor the structure wood)
• Weeping moss (to put on structure wood)
• Small java fern and anubias bonsai (to put on structure wood)
• Staurogyne repens and lobelia cardinalis mini for foreground, rotala rotundifolia and cryptocoryne for the back 
• Red root floaters (for shade and water disruption) 
• Water fertiliser (do I really need this? I really don't want fast-growing plants since the tank is so small) 
• Water dechlorinate / conditioner 
• Test kit 

My friend will be giving me some of her water and filter media so that I already have a healthy bacterial / nitrate cycle going. 
 
My main concerns are: algae, tank cleaning (including how often??), how to remove faeces etc.

Here’s the beautiful betta she’s gifting me (it’s currently in a disposable thingy because it was a colleague that gifted it to her):