Can i use 5 beacons and keep distance of any two beacon less than 4metres?
You mean you want to put 2 beacons on a single wall, and one beacon per each other wall? Yup, you can do that.
For maximum accuracy, it’s best to spread out the beacons evenly along the walls. For example, if you have a 12 m long wall, it’d be best to put one beacon 4 m from the corner, and another beacon 4 m from that one. If you put them closer together, nothing bad will happen, it just won’t be most optimal.