Siddhanth came from a set behind to post a 5-7 6-1 6-3 win to make the semifinals of the hard court event.
In another quarter-final, second seed Abhimanyu Vannemreddy overcame a second-set lapse to beat Dev V Javia 6-1 4-6 6-1.
Fourth seed Megh Kumar Patel was the most impressive player on court as he humbled Arjun Honappa 6-4 6-1 and Dhashines Suresh beat Naithaolin Golmei 6-2 6-3.
Fifth seed Prinkle Singh shocked second seed and error-prone Shaikh Humera 6-2 6-1.
In the boys under-14 event, top seed Aaryan Zaveri needed to play sharp tennis to beat Nishant Dabas 6-2 7-6 (6) third seed VM Sandeep had a few anxious moments before taming Nitin Jaipal Singh 6-4 1-6 6-3.
In the another quarter-final, Ajay Malik had a long day out before dismissing Denim Yadav 6-4 5-7 6-4.
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