It is recommended to recite "Ash hadu Anna Aliyyan Waliyullah" in the Adhan, but not with the intention that it is part of the adhan. It is recommended just like reciting the blessing upon the Holy Prophet (the Salawat) after mentioning his name in the adhan.
A believer should aim to fulfill the religious responsibilities of upholding the orders of the Sharia; one of them is learning the Islamic laws and teaching them. This could be achieved by learning more about the religion – and not necessarily reaching the level of ijtihad – by which a believer could serve Islam. One could serve the religion and be a role model amongst his society, family and friends by being obedient to the Islamic laws and by spreading the religious teachings in the areas where he resides. Therefore, ijtihad is not a goal that a student should have from the beginning. Ijtihad is a talent that can be achieved by studying and with the guidance of Almighty Allah. A student of Islamic studies should study hard and make use of his time as much as possible. If he achieves this, then he can thank Almighty Allah for this bounty. If he does not, he can still serve the religion.
There is no doubt that Almighty Allah protected the holy Quran from any changes or alterations and such protection played an important role in guarding the religion and protecting it from alterations and changes. The reason for that might be the fact that the verses of the Holy Quran were collected in one book and guarded during the lifetime of the Prophet (peace be upon him) and continued to be like that generation after generation until today.