if i welcome someone to my house, I would say あがってちょうだい。" please lift up " (the floor of Japanese house is a little bit higher than the ground. so "lift up a little bit" means "to come in the house" because of gap between floor and the ground.) On the other hand, the saying お入りください is more common because of the Japanese house or flat structure. there are getting decreasing the house with the gap between the floor and the ground. people refer the あがる as go upper and some people regard it as the polite phrase. if I waited someone for a long time for some reason and he come to my house, i would say "いらっしゃい。".. because there are some reason to invite him such as for providing dishes in restaurant. I hope this helps.

simply depended on your home air, you are under influence of grand parents or polite elder, you use お入りください or else, but you are not strictly trained polite habits like these days. you simply say どうぞ so there are not clear line, so you can choose. also depend on your attitude,not words.

いらっしゃい、どうぞ。is better. どうぞ（お上がりください。（おあがりください））＝ Please come in. You don't need to say "お上がりください” When we use "come into the house" in Japanese, we say おあがりください more polite than お入りください. When you use お入りください, the situation is you ask someone come into a room. Sorry for my poor English.Please come in