Praise be to Allah.
With regard to the first hadith, which is the hadith of Thawbaan, the freed slave of the Messenger of Allah (blessings and peace of Allah be upon him), it is a saheeh hadith.
It was narrated by an-Nasaa’i in his Sunan (3175) and classed as saheeh by al-Albaani in Saheeh an-Nasaa’i. It was also narrated by Ahmad in his Musnad (37/81), and classed as hasan by the commentators.
With regard to the second hadith, which is the hadith of Abu Hurayrah, it is a da‘eef (weak) hadith.
It was narrated by an-Nasaa’i (3173) and classed as da‘eef by al-Albaani in Da‘eef an-Nasaa’i. it was also narrated by Ahmad in his Musnad (12/28 – ar-Risaalah edition), and classed as da‘eef by the commentators. There are other isnaads for the hadith of Abu Hurayrah, all of which are da‘eef, and there are other hadiths on this topic that are not free of problems. What has been proven and established to be saheeh is the hadith of Thawbaan.
India was indeed invaded and taken over by the Muslims, and they destroyed its idols, on several occasions. That began at the time of al-Waleed ibn ‘Abd al-Malik, under the leadership of al-Qaasim ibn Muhammad ath-Thaqafi. It was also invaded and taken over at the time of the ‘Abbasids, under the leadership of the commander Mahmoud ibn Sabuktigin (may Allah have mercy on him). He took it upon himself to invade India once every year. Shaykh Siddeeq Hasan Khan (d. 1307 AH – may Allah have mercy on him) said:
With regard to India, it was conquered during the reign of al-Waleed ibn ‘Abd al-Malik, at the hands of Muhammad ibn Qaasim ath-Thaqafi in 92 AH, and his banners reached from the borders of Sindh to Kannauj in 95 AH. After he returned, the rulers of India returned to their places and the rulers among the Marwanid and ‘Abbasid caliphs remained in Sindh. … The author of al-Mughni said: … At the end of the fourth century AH, Sultan Mahmoud al-Ghaznawi set out to invade India, and he came several times; he was victorious and he captured war booty, and he wrested Sindh from the governors of the ‘Abbasid caliph al-Qaadir Billah ibn al-Muqtadir. But Sultan Mahmoud did not stay in India. His sons controlled a region stretching from Ghazneen to Lahore until the Sultan Mu‘izz ad-Deen Saam al-Ghuri took over Ghazneen, and came to Lahore and captured Khusrau Malik, who was the last ruler the Ghaznawi dynasty. He seized control of India and made Delhi the seat of government in 589 AH. From that date until the end of the twelfth century, the kingdoms of India were in the hands of Muslim Sultans.
Abjad al-‘Uloom (1/344-345).
Ibn Katheer (may Allah have mercy on him) said concerning the events of the year 94 AH: In that year, al-Qaasim ibn Muhammad ath-Thaqafi conquered India and captured booty that cannot be enumerated or described. Al-Bidaayah wa’n-Nihaayah (9/113)
Ibn Katheer (may Allah have mercy on him) said concerning the events of 96 AH: In that year, Yameen ad-Dawlah – Mahmoud ibn Sabuktigin – invaded India, conquering major cities and seizing a large amount of booty. He took captive one of their kings – namely the king of Karachi – who fled when he conquered it, and he broke their idols.
Al-Bidaayah wa’n-Nihaayah (11/358).
He also (may Allah have mercy on him) said concerning the events of 149 AH: in that year, Mahmoud ibn Sabuktigin invaded India, and met the king of India in battle. There was a great deal of fighting among the people, then the fighting ended with a great defeat for India, and the Muslims killed many of them and captured a great deal of booty from them, including gemstones, gold and silver. They also took from them two hundred elephants and they tried to pursue those who fled the battlefield, and destroyed many temples. Al-Bidaayah wa’n-Nihaayah (12/8)
What happened of the invasion of India is one of the signs of Prophethood, because the Prophet (blessings and peace of Allah be upon him) foretold its happening. This was knowledge of the unseen that Allah revealed to him. Ustadh Muhammad ‘Abd al-Wahhaab Buhayri (may Allah have mercy on him) said: It should be noted: the hadith mentioned – i.e., the hadith of Thawbaan – is one of the signs of Prophethood. The Muslims invaded India and Sindh at the time of the Umayyads – then he mentioned some incidents that occurred during the invasion and conquest of India. Buloogh al-Amaani min Asraar al-Fath ar-Rabbaani (22/411)
There is nothing to indicate that there will be another invasion of India that will occur at the end of time, close to the onset of the Hour or during the time of ‘Eesaa (peace be upon him), as was suggested by some scholars. Rather what appears to be the case is that what is referred to in the hadith is what actually happened. The hadith of Thawbaan does not mention the connection between the two groups; rather each group has its own time, although both of them may share the same virtue.
And Allah knows best.