Best Phones Under Rs. 9999 there are too many Options to choose from. There are some latest mobiles under Rs. 8000 that even offer up to 5,000mAh Battery or Dual Rear Camera setup or Powerfull Helio P60 processor, Snapdragon processor ETC. 
The below list contains all the latest mobile phones within the range of 9999 which offer the best value for money.

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Asus ZenFone Lite L1 at Rs. 5999: 

2 GB RAM & 16 GB ROM With Expandable Up to 256 GB
13.84 cm (5.45 inch) HD+ Display
13MP Rear Camera | 5MP Front Camera
3000 mAh Battery
Qualcomm Snapdragon 430 Processor

Buy From Here: Flipkart

Redmi 6A at Rs. 6499:

13MP rear camera | 5MP front camera
13.8 centimetres (5.45-inch) HD+ multi-touch capacitive touchscreen with 1440 x 720 pixels resolution, 295 PPI pixel density and 18:9 aspect ratio
Memory, Storage and SIM: 2GB RAM | 32GB internal memory expandable up to 256GB | Dual SIM (nano+nano) dual-standby (4G+4G)
An android v8.1 operating system with 2.0GHz MediaTek Helio A22 quad-core processor
3000mAH lithium-ion battery

Buy From Here: Amazon

Redmi 6 at Rs. 7999:

3 GB RAM | 32 GB ROM | Expandable Upto 256 GB
13.84 cm (5.45 inch) HD+ Display
12MP + 5MP | 5MP Front Camera
3000 mAh Lithium-polymer Battery
2.0 GHz Mediatek P22 Octacore Processor

Buy From Here: Flipkart

Realme C1 at Rs. 7499:

2 GB RAM | 32 GB ROM | Expandable Up to 256 GB
15.75 cm (6.2 inch) HD+ Display
13MP + 2MP | 5MP Front Camera
4230 mAh Li-ion Battery
Qualcomm Snapdragon 450 Octa Core 1.8 GHz Processor
2019 Edition
Face Unlock

Buy From Here: Flipkart

Lenovo K9 at Rs. 8999:

3 GB RAM | 32 GB ROM | Expandable Upto 256 GB
14.48 cm (5.7 inch) HD+ Display
13MP + 5MP | 13MP + 5MP Dual Front Camera
3000 mAh Battery
MediaTek P22 Processor

Buy From Here: Flipkart

Asus ZenFone Max M2 at Rs. 9999:

3 GB RAM | 32 GB ROM | Expandable Up to 2 TB
15.9 cm (6.26 inch) HD+ Display
13MP + 2MP | 8MP Front Camera
4000 mAh Battery
Qualcomm Snapdragon 632 Octa Core Processor

Buy From Here: Flipkart

Nokia 5.1 Plus at Rs. 9999: 

3 GB RAM | 32 GB ROM | Expandable Upto 400 GB
14.73 cm (5.8 inch) HD+ Display
13MP + 5MP | 8MP Front Camera
3060 mAh Battery
MediaTek Helio P60 Processor

Buy From Here: Flipkart

Redmi Y2 at Rs. 8999:

Camera: 12+5 MP Dual rear camera | 16 MP front camera
Display: 15.21 centimetres (5.99-inch) HD+ full-screen capacitive touchscreen display with 1440x720 pixels, 269 PPI pixel density and 18:9 aspect ratio
Memory, Storage & SIM: 3GB RAM | 32GB storage expandable up to 256GB with dedicated slot | Dual nano SIM with dual standby (4G+4G)
Operating System and Processor: Android v8.0 Oreo operating system with 2.0GHz Qualcomm Snapdragon 625 octa-core processor
Battery: 3080 mAH Lithium Polymer battery
Warranty: 1-year manufacturer warranty for device and 6 months manufacturer warranty for in-box accessories including batteries from the date of purchase
Included in the box: Power adaptor, USB Cable, Clear soft case

Buy From Here: Amazon 

Honor 7C at Rs. 8499: 

Camera: 13+2 MP Dual rear camera | 8 MP front camera with f2.0 aperture with soft selfie toning light. The charging time is 3 hours
Display: 15.2 centimetres (5.99-inch) HD+ Full view LED capacitive touchscreen display with 720x1440 pixels, 268 PPI pixel density and 18:9 aspect ratio
Memory, Storage & SIM: 3GB RAM | 32GB storage expandable up to 256GB with dedicated slot | Dual nano SIM with dual standby (4G+4G)
Operating System and Processor: Android v8.0 EMUI Oreo operating system with 1.8GHz Qualcomm Snapdragon 450 octa-core processor
Battery: 3000 mAh Lithium Polymer battery providing talk-time of 16 hours with stand by up to 349 hours
Warranty: 1-year manufacturer warranty on the handset and 6 months on battery/charger, 3 months on accessories (data cable) provided by the manufacturer from date of purchase
Included in the box: Charger, USB 2.0 cable, TP Protective film (Pre-applied)

Buy From Here: Amazon 

Samsung Galaxy M10 Starting Price Rs. 7999:

13MP+5MP ultra-wide angle dual camera | 5MP f2.0 front camera
15.8cm (6.22") HD+ Infinity V Display with 90% screen ratio
2GB RAM and 16GB internal memory expandable up to 512GB in a dedicated slot
Fast face unlock | 3400 mAh lithium-ion battery
Dual SIM (nano+nano) with dual standby and dual VoLTE
1.6GHz Exynos 7870 octa-core processor | Android Oreo v8.1 OS
1-year manufacturer warranty for device and 6 months manufacturer warranty for in-box accessories including batteries from the date of purchase

Buy From Here: Amazon