All 4G phones support 3G and most support 2G as well AFAIK. Only Jio uses 4G for voice (phone calls). Others like Airtel, Vodafone, Idea, all use 2G and/or 3G technology for voice and 4G for data.
Go to GSMArena (dot) com to check the exact specs of the phone you're interested in.
EDIT: By 'Featured Phone' do you mean feature phone? If that's the case, then the answer is, no such device exists to the best of my knowledge. Even if they come with 3G, they'll support UMTS, which is 3G Voice, whereas to access 3G data, you'll need HSPA.
Reliance Jio will reportedly launch a Rs. 1500 feature phone with 4G this month, but don't know too much about that.
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Like the above one with physical keys
My friend needs it for his abroad work.
Long battery standby & cheaper mobile.
Some countries ditching 2G soon
"All three telcos in Singapore - M1, Singtel and StarHub - will pull the plug on 2G services from Apr 1, 2017"