I will do drone and uav development with ardupilot and px4

Either. I can hand you a complete parts list with links and you order, or I source, build, test and ship the finished aircraft to you. Shipping, customs and any import duty are yours either way.

Both. Which one depends on your airframe, your sensors and how much you need to customise. I will tell you which and why before we start, not after.

No. I build, tune, test and hand over documented. Flight operations, airspace permission and licensing stay with you, and they differ by country - check yours early, because it can change what is worth building.

Yes - visual-inertial odometry and SLAM. It is a significantly harder build than GPS waypoint flight and it belongs in the Premium package. Tell me the environment: indoors, under canopy and urban canyon are three different problems.

Mission Planner is fine for testing and for engineers. If your operators are not engineers, or you need it in a browser or on a tablet, you need custom software. That is what the Premium package covers.

Test flights carry risk. I stage the envelope so failures happen low and slow, and I document the test plan and the tuning. Airframe repair or replacement cost is not included in the package.

That depends on the radio, the antenna and the terrain, not on a single number anyone can quote you. Tell me the distance and the environment and I will tell you what it takes to get there.