Welcome to the forum, kanhlk!
One becomes a Sotapanna by comprehending the real nature of this world of 31 realms (Tilakkhana) by LEARNING that from an Ariya (Noble Person) who himself learnt from such a person. That lineage can be traced back the Buddha Gotama.
On the other hand, one becomes a Buddha by DISCOVERING the real nature of this world by himself.
Once one becomes a Sotapanna, there is no need to figure out the real nature of this world himself. Thus, by definition, a Sotapnna (or one with higher magga phala) CANNOT become a Buddha.
You said: “Jotipala became a monk and delivered Buddhdharma for many of the others person who were there at Kassapa Budhdha Shasana, he had good knowledge
If that is so i really can’t undestand what actually prevent him at least became sothapana during that time ?”
As pointed out above, IF Jotipala attained the Sotapanna stage, he would not be able become a Buddha. Furthermore, one who is making “paramita” to become a Buddha will not “accidentally” or otherwise attain any magga phala on the way.
You also asked how one can identify the true Sotapanna stage. There are many posts at the site on that. Do a Search using the Search box at top right with “Sotapanna” and you will get many relevant posts. But here is one: “How Does One Know whether the Sotapanna Stage is Reached?“.