Bhagwaan Hanuman's divinity is unquestionable. Depending upon the scriptures, he is either the son of the wind god (vayu putr) or either a full or a partial avataram or manifestation of bhagwaan Shiv Shankar himself as says some questions and answers on this site. In some cases he is the avataram of Shiv ji's vahan, Shri Nandi.
Skanda Purana >> Book 1 - Māheśvara-khaṇḍa >> Kedar Khanda >> Chapter 8
शिलादतनयो नंदी शिवस्यानुचरः प्रियः ॥ ९९ ॥यो वै चैकादशो रुद्रो हनूमान्स महाकपिः ।
अवतीर्णः सहायार्थं विष्णोरमिततेजसः ॥ १०० ॥
Naṇḍī, the son of Śilāda, who was a favourite follower of Śiva, incarnated as the great monkey Hanūmān for rendering assistance to Viṣṇu of unmeasured splendour.
Now as regards Hanumaan ji being capable of granting boons and desires.
Several scriptures obviously recommends and dicuss elaborate ritual procedures on Hanuman ji's worship. Narada Purana is one of them.
Narada Purana >> Purvardha >> Chapter 74
सनत्कुमार उवाच ।।
अथोच्यंते हनुमतो मंत्राः सर्वेष्टदायकाः ।।
यान्समाराध्य विप्रेंद्र तत्तुल्याचरणा नराः ।। ७४-१ ।।
Shri Sanat Kumar ji said - ".Now, I shall mention the mantras of Hanuman. They are the bestowers of all desired things. O leading brahmin, by propitiating them men are able to perform tasks similar to those performed by Hanuman."
In the same chapter at the final verses
जप्तो युद्धे जयं दद्याद्व्याधौ व्याधिविनाशनः ।।
एवं यो भजते मंत्री वायुपुत्रं कपीश्वरम् ।। ७४-१९९ ।। सर्वान्स लभते कामान्दे वैरपि सुदुर्लभान् ।।धनं धान्यं सुतान्पौत्रान्सौभाग्यमतुलं यशः ।। ७४-२०० ।। मेधां विद्यां प्रभां राज्यं विवादे विजयं तथा ।।वश्याद्यानि च कर्माणि संगरे विजयं तथा ।। ७४-२०१ ॥उपासितोंऽजनागर्भसंभूतः प्रददात्यलम्।। ७४-२0२ ।।
When repeated, the mantra shall accord victory in the battle, in sickness it destroys the ailments. The repeater of the mantra who worships the lord of the monkeys attains all desires, is difficult of access even to Devas. He shall obtain wealth, grain, son, grandson, good fortune, unequalled renown, intellect, learning, lustre, kingdom, victory in arguments, acti¬ vities facilitating the control of people and victory in the battle. When duly worshipped the deity born of the womb of Anjana (i.e. Hanuman) bestows these things in sufficient quantity
https://archive.org/details/dli.bengal.10689.21516/page/n161/mode/1up